I’ve heard many mention there is no difference between the two. Will a 6v coil with a ballast resistor last, or is the double of current going to fry it? I’m a tight ass, I don’t want to buy a 6volt battery, nor a 12 volt coil. I want to run a engine for about 30/40 minutes on a stand to see what’s up with it. I also don’t want to damage the coil. I want my buddy who needs a turnkey engine, to just drop it in and connect some wires. Thanks.
Yes, it will do fine with a ballast. If you run a ballast, you are not doubling the voltage. Truthfully the main reason for a ballast wire, ballast resistor or a "resistor coil", is to protect the points.
Yes, understand I’m not doubling voltage, but will double the current. Well, wait a second, maybe not. The 6v set up had no ballast resistor, so I’d I use a ballast resistor the same as the coil I guess it would be the same voltage. Damn, I must quit asking questions when I get home from work, and wait till a night off, knock a few back and think Thanks for the eye opening!
I tell you what I did when I was kid to my 50 Coupe. I was a dumb kid back then. This before I got old and stupid. The car was converted to 12V. Basically, all they did was put a 12V battery in it, reverse the polarity and change some bulbs. The ignition was not ballasted. It was straight wired like a 6-volt car. It ran and drove. I corrected it with putting a ballast block between the coil and distributor. Yeah. The correct place for the ballast is on the ignition wire before the coil.... That car ran fire for years. On the F-1 I had a ballast burn out, lost ignition. I bypassed the ballast to get home. Points ignitions can run a little while off of straight 12V.... Most post 1955 factory wiring gives a full 12V on Start and then the ignition runs through the ballast. This feature is not necessary on a 6V to 12 conversions. It will do fine with the ignition resisted.
When I built my avatar pickup with flathead power, I converted to 12 volts. I put a ballast resistor in the ignition wire before the coil. I figured that would reduce the input to 6 volts and everything would be fine. The 6 volt coil burned out in short order. Fortunately I had another 6 volt coil on hand but it burned out very quickly as well. I put in a 12 volt coil and it has worked flawlessly for 22 years. I still don't understand why the 6 volt coil didn't work.
Wire size is rated for current(amp) capacity. Insulation size/type is rated for voltage capacity. Too much current in too small a wire, it overheats. Too much voltage for a given insulation can cause it to break down.
Again, JUST talking a ballast resistor...yes, a 6v vs 12v will work just fine under the same circumstances. When using a magneto...don't know. Been there, done that. Mike
Well, it's a bit complicated, the answer both is and isn't the same current (for a ballast resistor with the same resistance as the coil). With a ballast resistor the total voltage will divide between the coil, proportional to the resistances, if they're both the same the voltage will divide equally, 6V on each. In part this is true. The other half of the story is that the coil has impedance, in effect resistance that only comes into play when the voltage/current is changing, and with the points opening and closing when the engine runs that's a big part of what's going on. So, when the points first close the coil will act as it has a very large resistance, putting almost all of the 12V over the coil and very little on the ballast. Then, as the current rises less voltage goes to the coil and more to the ballast, after a while you get to the situation where no more change happens and it stabilises at 6V each. This means the coil starts out at high voltage, the current rises much faster than it would at a steady 6V, so you have forced the coil to get fully charged = ready for a full strength spark in far less time. Congratulations, you have made an ignition system that is fast enough to supply strong sparks at higher rpm, without increasing the peak current, so you won't overheat the coil even at low rpm when the points are closed a long time and current flows far longer than necessary to charge the coil.
This what I always thought. Points run on 6 volts even in a 12 volt car. The ballast reduces the 12 volt coil to 6 volts. When the car is cranking the ballast is by past to give a full 12 volts, then back to 6 volts when the car is running. Correct me if thats not right.
You are correct....pretty much. There are variables. The ballast may not exactly reduce the voltage in half. What is does do is reduce the 12V enough. Cranking on 12V requires it little more wiring. It's really not necessary as a car can crank fine on 6V (6VCars) and ballasted 12V(6Vcars with ballast).
The lower voltage of the coil is so when the starter pulls the battery voltage down the coil still has a good spark and the resister is to help the coil live. I remember Chrysler electronic ignitions in the 70s that would not work if the cranking battery voltage dropped much below 10v The starter would crank OK but no spark. Hook up a battery charger and it would start right up.
Where's Bubba when we need him. I am not the electric wizzard here, but its all about the resistance (OHMs in the coil. Not really any such thing as a 12 volt, or 6 volt coil, many are not marked, and you need to check the resistance from the primary wire to see what voltage its going to give the points . Again, not the expert here, but please correct me if wrong
That’s what started this topic. I’d heard what you’ve said, no difference, but have had could marked 12v. Have to see Hera what the one I have now is marked. Edit. Seems my spelling skills are lacking
12V coils have the resistance built into the coil you don't have the option of bypassing it resister during cranking
There are folks here that know a LOT more than me. But, I think the dropping voltage is the wrong way to really understand the function of the resistor. Voltage is part of the math, as is the resistance, but the name of the game is controlling the amperage flow through the points to prevent pitting and over heating. The max current that seems to be agreed that they can carry is about 4. Voltage available is 12, or close during normal running. Some combination of the coils primary resistance and external ballast resistor can be used to get to 4 amps. Most coils labeled for 12v and no added resistance have a more turns in the winding, not an internal resistor. Coils I've tested typically are about 1.5Ohm or about 3.5, depending on their intended usage.
OK Coils for dummies.... Like me. When the industry went to 12V in the 1950s the ignition system was ballasted or resisted from "12V battery hot". Chevy and Chrysler accomplished this with a porcelain "ballast block". Ford eventually used a "ballast wire" that reduced the "whatever" current to the coil. Also, there are specially marked resistor coils that the "ballast or resistor" is inside the coil. In short where the rubber meets the road for a dummy like me, there is no practical difference in a 12V or 6V coil. In a 6V car....no need for a ballast. In a 12V car....the ignition needs a ballast. So....the coils are practically the same. (same, same but different) Likely the biggest difference is one is marked 12V the other marked 6V. Exception is the resistor coil. These can be used in a 6V to 12V car without a ballast as all of "that" is accomplished in the coil. In my opinion the simpler solution for a 12V conversion is to use a ballast or ballast wire like most of the manufacturers did and not rely on a "resistor coil" that's more complicated inside than a "standard coil".
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